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[PATCH]: New sparse bitmap implementation


The attached patch implements a new sparse bitmap type for gcc.  The
main advantage over linked list bitmaps is twofold:

1. Individual bit testing is much faster, particularly for bits that
are in completely zero words.
2. Because it uses a contiguous array to store the bits, it has much
better locality for other operations (they are also easily
vectorizable).  The _into versions (almost) only touch words in the
contiguous array if the bits will exist in the destination (otherwise,
they just touch the wordmask).

Testing shows it to be about 50-60% faster on random bit testing than
our current sparse bitmap implementation.

Memory use currently depends on what the highest set bit is, which
means it can be worse than bitmaps in terms of overhead in weird
cases, but this is fixable by changing the word mask to be a bitmap
instead of an sbitmap (more testing is necessary speed wise before
doing this).

This is just an initial implementation.  There are plenty of
optimizations that can be done to the various operations to make them
faster.

Bootstrapped and regtested on i686-pc-linux-gnu, i386-darwin, and
x86-64-linux-gnu.

Okay for mainline?

2007-03-20 Daniel Berlin <dberlin@dberlin.org>

	* ebitmap.h: New file
	* ebitmap.c: New file
	* Makefile.in (ebitmap.o): New target.
Index: gcc/ebitmap.c
===================================================================
--- gcc/ebitmap.c	(revision 0)
+++ gcc/ebitmap.c	(revision 0)
@@ -0,0 +1,1019 @@
+/* Sparse array-based bitmaps.
+   Copyright (C) 2006 Free Software Foundation, Inc.
+   Contributed by Daniel Berlin <dberlin@dberlin.org>
+
+This file is part of GCC.
+
+GCC is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free
+Software Foundation; either version 2, or (at your option) any later
+version.
+
+GCC is distributed in the hope that it will be useful, but WITHOUT ANY
+WARRANTY; without even the implied warranty of MERCHANTABILITY or
+FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING.  If not, write to the Free
+Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
+02110-1301, USA.  */
+
+#include "config.h"
+#include "system.h"
+#include "coretypes.h"
+#include "tm.h"
+#include "rtl.h"
+#include "flags.h"
+#include "obstack.h"
+#include "ebitmap.h"
+
+/* The ebitmap data structure is a sparse bitmap structure that works
+   by having two pieces:
+   1. An array of all non-zero words in the structures, organized as
+   an array of HOST_WIDE_INT's.
+   2. A non-sparse bitmap saying which bitmap words are present in the
+   array.
+
+   As a consequence of this representation, testing whether a bit
+   exists in the bitmap is faster than linked-list bitmaps.  For bits
+   in words that are all zero, the time to test is O(1).  For bits
+   in words that exist, it requires it will require O(n/sizeof(word))
+   time to perform the test (ignoring the one element cache).
+   It also has much better locality than linked list bitmaps.
+
+   To test whether a bit exists, we do the following:
+   1. Test whether the word the bit would appear in exists in the
+   bitmap (O(1) check of the mask).  If not, fail.
+
+   2. Population count the mask up to the word containing the bit, to
+   find the place in the array the word would be (popcount is cached,
+   but this is just as slow as the linked list bitmap)
+   3. Test the word to see if the bit exists.
+
+   Just like linked list bitmaps, we cache the last element that has
+   been tested in order to speed up common access patterns.
+
+   Most of the other speedups are simply due to better locality of the
+   single contiguous array.
+
+   As would be expected in a structure like this, insertion into an
+   empty word in the middle requires moving bits to make room for the
+   new word.   As most operations that perform sets perform them in
+   order, this is rarely a problem.  We also take advantage of the
+   same element cache to make repeated sets to the same word O(1).
+
+   Operations on the entire bitmap are also more efficient than
+   bitmaps, as they are all operating on contiguous memory, and can be
+   easily vectorized.  They are all O(number of words) + O(number of
+   bits that may end up in the destination), as the approriate
+   operation is first performed on the word mask, and then only those
+   elements that may generate results are touched.
+
+   Memory wise, the ebitmap starts out using less memory than the
+   linked list bitmap, but it's size in memory is technically bounded
+   by (size of the highest set bit) / (size of a word).  This is
+   because the mask is non-sparse.  The mask could be transformed into
+   a sparse bitmap at the cost of making bit testing *theoretically*
+   slower (real world numbers have not been computed yet as to whether
+   it matters or not).  */
+
+/* #define EBITMAP_DEBUGGING  */
+
+/* Find the last set bit in EBITMAP map.  */
+
+unsigned int
+ebitmap_last_set_bit (ebitmap map)
+{
+  unsigned int i = 0;
+  ebitmap_iterator ebi;
+
+  /* This is not the fastest way to do this, we could simply look for
+     the popcount, and start there, but this function is not used
+     anywhere speed critical.  */
+  EXECUTE_IF_SET_IN_EBITMAP (map, 0, i, ebi);
+
+  return i;
+}
+
+/* Grow or shrink the internal word array for MAP to NEWSIZE
+   elements.  */
+
+static inline void
+ebitmap_array_grow (ebitmap map, unsigned int newsize)
+{
+  if (newsize <= map->n_elts)
+    {
+      map->n_elts = newsize;
+      return;
+    }
+
+  newsize += newsize / 4;
+
+  map->n_elts = newsize;
+  map->elts = xrealloc (map->elts, sizeof (EBITMAP_ELT_TYPE) * newsize);
+}
+
+/* Grow the internal word array for MAP so it is at least SIZE
+   elements.  Will not shrink the array if it is already big
+   enough.  */
+
+static inline void
+ebitmap_array_maybe_grow (ebitmap map, unsigned int size)
+{
+  if (size >= map->n_elts)
+    ebitmap_array_grow (map, size + 1);
+}
+
+/* Retrieve the IDX'th element from the word array for MAP.  */
+
+static inline EBITMAP_ELT_TYPE
+ebitmap_array_get (ebitmap map, unsigned int idx)
+{
+  gcc_assert (idx < map->n_elts);
+  return map->elts[idx];
+}
+
+/* Retrieve a pointer to the IDX'th element from the word array for
+   MAP.  If the element index is greater than the size of the array,
+   the array will be grown to the correct size.  */
+
+static inline EBITMAP_ELT_TYPE *
+ebitmap_array_grow_get (ebitmap map, unsigned int idx)
+{
+  if (idx >= map->n_elts)
+    ebitmap_array_grow (map, idx + 1);
+  return &map->elts[idx];
+}
+
+/* Initialize the internal word array for MAP, so that it is SIZE
+   elements.  */
+
+static inline void
+ebitmap_array_init (ebitmap map, unsigned int size)
+{
+  if (size > 0)
+    {
+      map->elts = xmalloc (sizeof (EBITMAP_ELT_TYPE) * size);
+      map->n_elts = size;
+    }
+  else
+    {
+      map->n_elts = 0;
+      map->elts = NULL;
+    }
+}
+
+/* Free the internal word array for MAP.  */
+
+static inline void
+ebitmap_array_clear (ebitmap map)
+{
+  free (map->elts);
+  map->elts = NULL;
+  map->n_elts = 0;
+}
+
+/* Clear ebitmap MAP.  */
+
+void
+ebitmap_clear (ebitmap map)
+{
+  ebitmap_array_clear (map);
+  sbitmap_zero (map->wordmask);
+  map->wordmask = sbitmap_resize (map->wordmask, 1, 0);
+  map->numwords = 0;
+  map->cache = NULL;
+  map->cacheindex = 0;
+}
+
+ebitmap
+ebitmap_alloc (unsigned int size)
+{
+  ebitmap ret = xmalloc (sizeof (struct ebitmap_def));
+  if (size == 0)
+    size = EBITMAP_ELT_BITS;
+  ebitmap_array_init (ret, size / EBITMAP_ELT_BITS);
+  ret->wordmask = sbitmap_alloc_with_popcount (size);
+  sbitmap_zero (ret->wordmask);
+  ret->numwords = 0;
+  ret->cache = NULL;
+  ret->cacheindex = 0;
+
+  return ret;
+}
+
+/* Clear BIT from ebitmap MAP.  */
+
+void
+ebitmap_clear_bit (ebitmap map, unsigned int bit)
+{
+  unsigned int wordindex = bit / EBITMAP_ELT_BITS;
+  unsigned int eltwordindex;
+  unsigned int bitindex, shift;
+
+  /* If the bit can't exist in our bitmap, just return.  */
+  if (map->numwords == 0)
+    return;
+
+  if (wordindex >= map->wordmask->n_bits
+      || !TEST_BIT (map->wordmask, wordindex))
+    return;
+
+  eltwordindex = sbitmap_popcount (map->wordmask, wordindex);
+
+  bitindex = bit % EBITMAP_ELT_BITS;
+  shift = bitindex;
+
+  map->elts[eltwordindex] &= ~(((EBITMAP_ELT_TYPE)1) << shift);
+
+  /* Clear out the empty words.  */
+  if (map->elts[eltwordindex] == 0)
+    {
+      unsigned int ix;
+
+      if (map->cache != NULL && map->cacheindex == eltwordindex)
+	map->cache = NULL;
+
+      RESET_BIT (map->wordmask, wordindex);
+
+      for (ix = eltwordindex; ix < map->numwords-1; ix++)
+	map->elts[ix] = map->elts[ix + 1];
+      map->numwords--;
+    }
+}
+
+/* Set BIT in ebitmap MAP.  */
+
+void
+ebitmap_set_bit (ebitmap map, unsigned int bit)
+{
+  unsigned int wordindex = bit / EBITMAP_ELT_BITS;
+  unsigned int eltwordindex;
+  unsigned int bitindex;
+
+
+  /* If we have this element cached, just set the bit in it.  */
+  if (map->cache && map->cacheindex == wordindex)
+    {
+      (*map->cache) |= (EBITMAP_ELT_TYPE)1 << bitindex;
+      return;
+    }
+
+  /* Resize the wordmask if necessary.  */
+  if (wordindex >= map->wordmask->n_bits)
+    map->wordmask = sbitmap_resize (map->wordmask, wordindex + 1, 0);
+
+  /* Allocate a new word in the array and move whatever is in it's
+     place, if necessary. */
+  if (!TEST_BIT (map->wordmask, wordindex))
+    {
+      unsigned long count;
+      unsigned int i;
+
+      SET_BIT (map->wordmask, wordindex);
+      count = sbitmap_popcount (map->wordmask, wordindex);
+      gcc_assert (count <= map->numwords);
+
+      for (i = map->numwords; i > count; i--)
+	{
+	  EBITMAP_ELT_TYPE *newelt;
+	  newelt = ebitmap_array_grow_get (map, i);
+	  *newelt = ebitmap_array_get (map, i - 1);
+	}
+      map->numwords++;
+      eltwordindex = count;
+      ebitmap_array_maybe_grow (map, eltwordindex);
+      map->elts[eltwordindex] = 0;
+    }
+  else
+    {
+      eltwordindex = sbitmap_popcount (map->wordmask, wordindex);
+    }
+
+  /* Set the actual bit.  */
+  bitindex = bit % EBITMAP_ELT_BITS;
+
+  map->elts[eltwordindex] |= (EBITMAP_ELT_TYPE)1 << bitindex;
+  map->cache = &map->elts[eltwordindex];
+  map->cacheindex = wordindex;
+}
+
+
+/* Return true if MAP contains BIT.  */
+
+bool
+ebitmap_bit_p (ebitmap map, unsigned int bit)
+{
+  unsigned int wordindex = bit / EBITMAP_ELT_BITS;
+  unsigned int bitindex= bit % EBITMAP_ELT_BITS;
+
+  /* Trivial empty ebitmap case.  */
+  if (map->numwords == 0)
+    return false;
+
+  if (map->cache && map->cacheindex == wordindex)
+    return ((*map->cache) >> bitindex) & 1;
+
+  /* If the wordindex is greater than the size of the wordmask, *or*
+     it's not set in the wordmask, this bit can't exist in our
+     ebitmap.  */
+  if (wordindex >= map->wordmask->n_bits
+      || !TEST_BIT (map->wordmask, wordindex))
+    return false;
+
+  /* Find the bit and test it.  */
+  map->cacheindex = wordindex;
+  wordindex = sbitmap_popcount (map->wordmask, wordindex);
+  map->cache = &map->elts[wordindex];
+
+  return (map->elts[wordindex] >> bitindex) & 1;
+}
+
+/* Copy ebitmap SRC to DST.  */
+
+void
+ebitmap_copy (ebitmap dst, ebitmap src)
+{
+  /* Blow away any existing wordmask, and copy the new one.  */
+  sbitmap_free (dst->wordmask);
+  dst->wordmask = sbitmap_alloc_with_popcount (src->wordmask->n_bits);
+  sbitmap_copy (dst->wordmask, src->wordmask);
+
+  /* Make sure our destination array is big enough, and then copy the
+     actual words.  */
+  ebitmap_array_grow (dst, src->numwords);
+  memcpy (dst->elts, src->elts,
+	  src->numwords * sizeof (EBITMAP_ELT_TYPE));
+  dst->numwords = src->numwords;
+  dst->cache = NULL;
+}
+
+/* Dump ebitmap BMAP to FILE.  */
+
+void
+dump_ebitmap (FILE *file, ebitmap bmap)
+{
+  unsigned int pos;
+  unsigned int i;
+  int res;
+  unsigned int size;
+
+  res = sbitmap_last_set_bit (bmap->wordmask);
+  if (res == -1)
+    size = 0;
+  else
+    size = (res + 1) * EBITMAP_ELT_BITS;
+
+  fprintf (file, "n_words = %d, set = {", bmap->numwords);
+
+  for (pos = 30, i = 0; i < size; i++)
+    if (ebitmap_bit_p (bmap, i))
+      {
+	if (pos > 70)
+	  {
+	    fprintf (file, "\n  ");
+	    pos = 0;
+	  }
+
+	fprintf (file, "%d ", i);
+	pos += 2 + (i >= 10) + (i >= 100) + (i >= 1000);
+      }
+
+  fprintf (file, "}\n");
+}
+
+/* Dump ebitmap BMAP to stderr.  */
+
+void
+debug_ebitmap (ebitmap bmap)
+{
+  dump_ebitmap (stderr, bmap);
+}
+
+/* Perform the operation DST &= SRC.  */
+
+void
+ebitmap_and_into (ebitmap dst, ebitmap src)
+{
+  sbitmap_iterator sbi;
+  unsigned int i;
+  unsigned int neweltindex = 0;
+  unsigned int dsteltindex = 0;
+  unsigned int srceltindex = 0;
+
+  gcc_assert (dst != src);
+
+  dst->cache = NULL;
+
+  /* Short circuit the empty bitmap cases.  */
+  if (src->numwords == 0 || dst->numwords == 0)
+    {
+      ebitmap_clear (dst);
+      return;
+    }
+
+  /* AND the masks, then walk the words that may actually appear in
+     the result, AND'ing them.  */
+  sbitmap_a_and_b (dst->wordmask, dst->wordmask, src->wordmask);
+
+  EXECUTE_IF_SET_IN_SBITMAP (dst->wordmask, 0, i, sbi)
+    {
+      bool srchasword;
+
+      /* If it really made a speed difference, we could iterate both
+	 masks in parallel so the src testing didn't look like random
+	 bittests.  */
+      srchasword = TEST_BIT (src->wordmask, i);
+
+      if (srchasword)
+	{
+	  EBITMAP_ELT_TYPE tmpword = ebitmap_array_get (src, srceltindex++);
+	  tmpword &= ebitmap_array_get (dst, dsteltindex++);
+	  if (tmpword != 0)
+	    {
+	      EBITMAP_ELT_TYPE *dstplace;
+	      dstplace = ebitmap_array_grow_get (dst, neweltindex++);
+	      *dstplace = tmpword;
+	    }
+	  else
+	    RESET_BIT (dst->wordmask, i);
+	}
+      else
+	{
+	  dsteltindex++;
+	  RESET_BIT (dst->wordmask, i);
+	}
+    }
+#ifdef EBITMAP_DEBUGGING
+  {
+    unsigned int i;
+
+    for (i = 0; i <  dst->numwords; i++)
+      gcc_assert (dst->elts[i] != 0);
+
+    verify_popcount (dst->wordmask);
+    gcc_assert (sbitmap_popcount (dst->wordmask,
+				  dst->wordmask->n_bits) == dst->numwords);
+    gcc_assert (ebitmap_last_set_bit (dst) < num_ssa_names);
+  }
+#endif
+  dst->numwords = neweltindex;
+}
+
+/* Perform the operation DST = SRC1 & SRC2.  */
+
+void
+ebitmap_and (ebitmap dst, ebitmap src1, ebitmap src2)
+{
+  sbitmap_iterator sbi;
+  unsigned int i;
+  unsigned int neweltindex = 0;
+  unsigned int src1eltindex = 0;
+  unsigned int src2eltindex = 0;
+
+  dst->cache = NULL;
+  if (src1->numwords == 0 || src2->numwords == 0)
+    {
+      ebitmap_clear (dst);
+      return;
+    }
+
+  dst->wordmask
+    = sbitmap_resize (dst->wordmask,
+		      MAX (src1->wordmask->n_bits, src2->wordmask->n_bits),
+		      0);
+  sbitmap_a_and_b (dst->wordmask, src1->wordmask, src2->wordmask);
+
+  EXECUTE_IF_SET_IN_SBITMAP (dst->wordmask, 0, i, sbi)
+    {
+      bool src1hasword, src2hasword;
+
+      src1hasword = TEST_BIT (src1->wordmask, i);
+      src2hasword = TEST_BIT (src2->wordmask, i);
+
+      if (src1hasword && src2hasword)
+	{
+	  EBITMAP_ELT_TYPE tmpword = ebitmap_array_get (src1, src1eltindex++);
+	  tmpword &= ebitmap_array_get (src2, src2eltindex++);
+	  if (tmpword != 0)
+	    {
+	      EBITMAP_ELT_TYPE *dstplace;
+	      dstplace = ebitmap_array_grow_get (dst, neweltindex++);
+	      *dstplace = tmpword;
+	    }
+	  else
+	    RESET_BIT (dst->wordmask, i);
+	}
+      else if (src1hasword)
+	src1eltindex++;
+      else
+	src2eltindex++;
+    }
+#ifdef EBITMAP_DEBUGGING
+  {
+    ebitmap_iterator ebi;
+    unsigned int i;
+
+    for (i = 0; i <  dst->numwords; i++)
+      gcc_assert (dst->elts[i] != 0);
+
+    EXECUTE_IF_SET_IN_EBITMAP (src1, 0, i, ebi)
+      if (ebitmap_bit_p (src2, i))
+	gcc_assert (ebitmap_bit_p (dst, i));
+
+    for (i = 0; i <  dst->numwords; i++)
+      gcc_assert (dst->elts[i] != 0);
+
+    verify_popcount (dst->wordmask);
+    gcc_assert (sbitmap_popcount (dst->wordmask,
+				  dst->wordmask->n_bits) == dst->numwords);
+    gcc_assert (ebitmap_last_set_bit (dst) < num_ssa_names);
+  }
+#endif
+  dst->numwords = neweltindex;
+}
+
+/* Perform the operation DST |= SRC.  */
+
+bool
+ebitmap_ior_into (ebitmap dst, ebitmap src)
+{
+  unsigned int dstsize = dst->wordmask->n_bits;
+  unsigned int srcsize = src->wordmask->n_bits;
+  sbitmap_iterator sbi;
+  unsigned int i;
+  sbitmap tempmask;
+  unsigned int neweltindex = 0;
+  unsigned int dsteltindex = 0;
+  unsigned int srceltindex = 0;
+  bool changed = false;
+  EBITMAP_ELT_TYPE *newarray;
+  unsigned int newarraysize;
+#ifdef EBITMAP_DEBUGGING
+  ebitmap dstcopy = ebitmap_alloc (1);
+  ebitmap_copy (dstcopy, dst);
+#endif
+
+  dst->cache = NULL;
+  if (dst == src)
+    return false;
+
+  if (dst->numwords == 0 && src->numwords != 0)
+    {
+      ebitmap_copy (dst, src);
+      return true;
+    }
+  else if (src->numwords == 0)
+    return false;
+
+  /* We can do without the temp mask if it's faster, but it would mean
+     touching more words in the actual dense vector.  */
+  tempmask = sbitmap_alloc (MAX (srcsize, dstsize));
+  sbitmap_zero (tempmask);
+  if (srcsize == dstsize)
+    {
+      sbitmap_a_or_b (tempmask, dst->wordmask, src->wordmask);
+    }
+  else
+    {
+      dst->wordmask = sbitmap_resize (dst->wordmask, MAX (srcsize, dstsize),
+				      0);
+      if (MAX (srcsize, dstsize) == srcsize)
+	{
+	  sbitmap_copy_n (tempmask, dst->wordmask, dst->wordmask->size);
+	  sbitmap_a_or_b (tempmask, tempmask, src->wordmask);
+	}
+      else
+	{
+	  sbitmap_copy_n (tempmask, src->wordmask, src->wordmask->size);
+	  sbitmap_a_or_b (tempmask, tempmask, dst->wordmask);
+	}
+    }
+  newarraysize = src->numwords + dst->numwords;
+  newarray = xmalloc (newarraysize * sizeof (EBITMAP_ELT_TYPE));
+
+  EXECUTE_IF_SET_IN_SBITMAP (tempmask, 0, i, sbi)
+    {
+      bool dsthasword, srchasword;
+
+      dsthasword = (i < dst->wordmask->n_bits
+		    && TEST_BIT (dst->wordmask, i));
+      srchasword = (i < src->wordmask->n_bits
+		    && TEST_BIT (src->wordmask, i));
+
+      if (dsthasword && srchasword)
+	{
+	  EBITMAP_ELT_TYPE tmpword = ebitmap_array_get (src, srceltindex++);
+	  tmpword |= ebitmap_array_get (dst, dsteltindex);
+	  if (!changed)
+	    changed |= tmpword != ebitmap_array_get (dst, dsteltindex);
+	  dsteltindex++;
+	  newarray[neweltindex++] = tmpword;
+	}
+      else if (dsthasword)
+	{
+	  newarray [neweltindex++] = ebitmap_array_get (dst, dsteltindex++);
+	}
+      else
+	{
+	  newarray [neweltindex++] = ebitmap_array_get (src, srceltindex++);
+	  gcc_assert (i < dst->wordmask->n_bits);
+	  SET_BIT (dst->wordmask, i);
+	  changed |= true;
+	}
+    }
+
+  sbitmap_free (tempmask);
+  if (changed)
+    {
+      dst->numwords = neweltindex;
+      free (dst->elts);
+      dst->elts = newarray;
+      dst->n_elts = newarraysize;
+    }
+  else
+    free (newarray);
+
+#ifdef EBITMAP_DEBUGGING
+  {
+    ebitmap_iterator ebi;
+    unsigned int i;
+
+    for (i = 0; i <  dst->numwords; i++)
+      gcc_assert (dst->elts[i] != 0);
+
+    EXECUTE_IF_SET_IN_EBITMAP (src, 0, i, ebi)
+      gcc_assert (ebitmap_bit_p (dst, i));
+    EXECUTE_IF_SET_IN_EBITMAP (dstcopy, 0, i, ebi)
+      gcc_assert (ebitmap_bit_p (dst, i));
+
+    verify_popcount (dst->wordmask);
+    gcc_assert (changed == !ebitmap_equal_p (dst, dstcopy));
+    gcc_assert (sbitmap_popcount (dst->wordmask,
+				  dst->wordmask->n_bits) == dst->numwords);
+    gcc_assert (ebitmap_last_set_bit (dst) < num_ssa_names);
+  }
+#endif
+  return changed;
+}
+
+/* Perform the operation DST = SRC1 | SRC2.  */
+
+bool
+ebitmap_ior (ebitmap dst, ebitmap src1, ebitmap src2)
+{
+  unsigned int src1size = src1->wordmask->n_bits;
+  unsigned int src2size = src2->wordmask->n_bits;
+  sbitmap_iterator sbi;
+  unsigned int i;
+  sbitmap tempmask;
+  unsigned int neweltindex = 0;
+  unsigned int src1eltindex = 0;
+  unsigned int src2eltindex = 0;
+  bool changed = false;
+  EBITMAP_ELT_TYPE *newarray;
+  unsigned int newarraysize;
+#ifdef EBITMAP_DEBUGGING
+  ebitmap dstcopy = ebitmap_alloc (1);
+  ebitmap_copy (dstcopy, dst);
+#endif
+
+  dst->cache = NULL;
+  tempmask = sbitmap_alloc_with_popcount (MAX (src1size, src2size));
+  sbitmap_zero (tempmask);
+  if (src1size == src2size)
+    {
+      sbitmap_a_or_b (tempmask, src1->wordmask, src2->wordmask);
+    }
+  else
+    {
+      if (MAX (src1size, src2size) == src1size)
+	{
+	  sbitmap_copy_n (tempmask, src2->wordmask, src2->wordmask->size);
+	  sbitmap_a_or_b (tempmask, tempmask, src1->wordmask);
+	}
+      else
+	{
+	  sbitmap_copy_n (tempmask, src1->wordmask, src1->wordmask->size);
+	  sbitmap_a_or_b (tempmask, tempmask, src2->wordmask);
+	}
+    }
+  newarraysize = src1->numwords + src2->numwords;
+  newarray = xmalloc (newarraysize * sizeof (EBITMAP_ELT_TYPE));
+
+  EXECUTE_IF_SET_IN_SBITMAP (tempmask, 0, i, sbi)
+    {
+      bool src1hasword, src2hasword;
+      EBITMAP_ELT_TYPE tmpword;
+      src1hasword = (i < src1->wordmask->n_bits
+		    && TEST_BIT (src1->wordmask, i));
+      src2hasword = (i < src2->wordmask->n_bits
+		    && TEST_BIT (src2->wordmask, i));
+
+      if (src1hasword && src2hasword)
+	{
+	  tmpword = ebitmap_array_get (src1, src1eltindex++)
+	    | ebitmap_array_get (src2, src2eltindex++);
+	  newarray[neweltindex++] = tmpword;
+	}
+      else if (src1hasword)
+	{
+	  tmpword = ebitmap_array_get (src1, src1eltindex++);
+	  newarray [neweltindex++] = tmpword;
+	}
+      else
+	{
+	  tmpword = ebitmap_array_get (src2, src2eltindex++);
+	  newarray [neweltindex++] = tmpword;
+	}
+
+      if (i >= dst->wordmask->n_bits ||!TEST_BIT (dst->wordmask, i))
+	{
+	  changed = true;
+	}
+      else if (!changed)
+	{
+	  unsigned int count = sbitmap_popcount (dst->wordmask, i);
+	  changed |= ebitmap_array_get (dst, count) != tmpword;
+	}
+    }
+
+  if (changed)
+    {
+      sbitmap_free (dst->wordmask);
+      dst->wordmask = tempmask;
+      dst->numwords = neweltindex;
+      free (dst->elts);
+      dst->elts = newarray;
+      dst->n_elts = newarraysize;
+    }
+  else
+    {
+      sbitmap_free (tempmask);
+      free (newarray);
+    }
+
+#ifdef EBITMAP_DEBUGGING
+  {
+    ebitmap_iterator ebi;
+    unsigned int i;
+
+    for (i = 0; i <  dst->numwords; i++)
+      gcc_assert (dst->elts[i] != 0);
+
+    EXECUTE_IF_SET_IN_EBITMAP (src1, 0, i, ebi)
+      gcc_assert (ebitmap_bit_p (dst, i));
+
+    EXECUTE_IF_SET_IN_EBITMAP (src2, 0, i, ebi)
+      gcc_assert (ebitmap_bit_p (dst, i));
+  }
+  verify_popcount (dst->wordmask);
+  gcc_assert (changed == !ebitmap_equal_p (dst, dstcopy));
+  gcc_assert (sbitmap_popcount (dst->wordmask,
+				dst->wordmask->n_bits) == dst->numwords);
+  gcc_assert (ebitmap_last_set_bit (dst) < num_ssa_names);
+#endif
+
+  return changed;
+}
+
+/* Perform the operation DST &= ~SRC.  */
+
+bool
+ebitmap_and_compl_into (ebitmap dst, ebitmap src)
+{
+  bool changed = false;
+  unsigned int i;
+  unsigned int neweltindex = 0;
+  unsigned int dsteltindex = 0;
+  sbitmap_iterator sbi;
+#ifdef EBITMAP_DEBUGGING
+  ebitmap dstcopy = ebitmap_alloc (1);
+  ebitmap_copy (dstcopy, dst);
+#endif
+
+  gcc_assert (dst != src);
+  dst->cache = NULL;
+  if (src->numwords == 0)
+    return false;
+
+  EXECUTE_IF_SET_IN_SBITMAP (dst->wordmask, 0, i, sbi)
+    {
+      bool srchasword;
+
+      srchasword = (i < src->wordmask->n_bits
+		    && TEST_BIT (src->wordmask, i));
+
+      if (srchasword)
+	{
+	  unsigned int srccount = sbitmap_popcount (src->wordmask, i);
+	  EBITMAP_ELT_TYPE tmpword = ebitmap_array_get (dst, dsteltindex);
+	  tmpword &= ~(ebitmap_array_get (src, srccount));
+	  if (!changed)
+	    changed |= ebitmap_array_get (dst, dsteltindex++) != tmpword;
+
+	  if (tmpword != 0)
+	    {
+	      EBITMAP_ELT_TYPE *dstplace;
+	      dstplace = ebitmap_array_grow_get (dst, neweltindex++);
+	      *dstplace = tmpword;
+	    }
+	  else
+	    RESET_BIT (dst->wordmask, i);
+	}
+      else
+	{
+	  dsteltindex++;
+	  neweltindex++;
+	}
+    }
+#ifdef EBITMAP_DEBUGGING
+  {
+    unsigned int i;
+    ebitmap_iterator ebi;
+
+    EXECUTE_IF_SET_IN_EBITMAP (dstcopy, 0, i, ebi)
+      {
+	if (!ebitmap_bit_p (src, i))
+	  gcc_assert (ebitmap_bit_p (dst, i));
+      }
+
+    for (i = 0; i <  dst->numwords; i++)
+      gcc_assert (dst->elts[i] != 0);
+
+    gcc_assert (sbitmap_popcount (dst->wordmask,
+				  dst->wordmask->n_bits) == neweltindex);
+    verify_popcount (dst->wordmask);
+    gcc_assert (changed == !ebitmap_equal_p (dst, dstcopy));
+    gcc_assert (sbitmap_popcount (dst->wordmask,
+				  dst->wordmask->n_bits) == dst->numwords);
+    gcc_assert (ebitmap_last_set_bit (dst) < num_ssa_names);
+  }
+#endif
+  dst->numwords = neweltindex;
+  /* sbitmap_popcount (dst->wordmask, -1); */
+
+  return changed;
+}
+
+/* Perform the operation DST = SRC1 & ~SRC2.  */
+
+bool
+ebitmap_and_compl (ebitmap dst, ebitmap src1, ebitmap src2)
+{
+  unsigned int src1size = src1->wordmask->n_bits;
+  sbitmap_iterator sbi;
+  unsigned int i;
+  sbitmap tempmask;
+  unsigned int neweltindex = 0;
+  unsigned int src1eltindex = 0;
+  bool changed = false;
+  EBITMAP_ELT_TYPE *newarray;
+  unsigned int newarraysize;
+
+  /* XXX: Optimize like the into version.  */
+  dst->cache = NULL;
+  tempmask = sbitmap_alloc_with_popcount (src1size);
+  sbitmap_zero (tempmask);
+  sbitmap_copy (tempmask, src1->wordmask);
+
+  newarraysize = src1->numwords;
+  newarray = xmalloc (newarraysize * sizeof (EBITMAP_ELT_TYPE));
+
+  EXECUTE_IF_SET_IN_SBITMAP (src1->wordmask, 0, i, sbi)
+    {
+      bool src2hasword;
+      EBITMAP_ELT_TYPE tmpword;
+
+      src2hasword = (i < src2->wordmask->n_bits
+		    && TEST_BIT (src2->wordmask, i));
+
+      if (src2hasword)
+	{
+	  unsigned int src2count = sbitmap_popcount (src2->wordmask, i);
+	  tmpword = ebitmap_array_get (src1, src1eltindex++)
+	    & ~(ebitmap_array_get (src2, src2count));
+	  if (tmpword)
+	    {
+	      newarray[neweltindex++] = tmpword;
+	    }
+	  else
+	    RESET_BIT (tempmask, i);
+
+	}
+      else
+	{
+	  tmpword = ebitmap_array_get (src1, src1eltindex++);
+	  gcc_assert (tmpword != 0);
+	  newarray[neweltindex++] = tmpword;
+	}
+
+      if (i >= dst->wordmask->n_bits || !TEST_BIT (dst->wordmask, i))
+	{
+	  changed = true;
+	}
+      else if (!changed)
+	{
+	  unsigned int count = sbitmap_popcount (dst->wordmask, i);
+	  changed |= ebitmap_array_get (dst, count) != tmpword;
+	}
+    }
+  if (changed)
+    {
+      sbitmap_free (dst->wordmask);
+      dst->wordmask = tempmask;
+      dst->numwords = neweltindex;
+      free (dst->elts);
+      dst->elts = newarray;
+      dst->n_elts = newarraysize;
+    }
+  else
+    {
+      free (tempmask);
+      free (newarray);
+    }
+#ifdef EBITMAP_DEBUGGING
+  {
+    unsigned int i;
+    ebitmap_iterator ebi;
+
+    EXECUTE_IF_SET_IN_EBITMAP (src1, 0, i, ebi)
+      {
+	if (!ebitmap_bit_p (src2, i))
+	  gcc_assert (ebitmap_bit_p (dst, i));
+      }
+  for (i = 0; i <  dst->numwords; i++)
+    gcc_assert (dst->elts[i] != 0);
+
+  verify_popcount (dst->wordmask);
+  gcc_assert (sbitmap_popcount (dst->wordmask,
+				dst->wordmask->n_bits) == dst->numwords);
+  gcc_assert (ebitmap_last_set_bit (dst) < num_ssa_names);
+  }
+#endif
+  return changed;
+}
+
+/* Perform the operation DST = A | (B & ~C).  */
+
+bool
+ebitmap_ior_and_compl (ebitmap dst, ebitmap a, ebitmap b, ebitmap c)
+{
+  bool changed;
+  ebitmap temp = ebitmap_alloc (1);
+#ifdef EBITMAP_DEBUGGING
+  ebitmap dstcopy = ebitmap_alloc (1);
+  ebitmap_copy (dstcopy, dst);
+#endif
+
+  dst->cache = NULL;
+  ebitmap_and_compl (temp, b, c);
+  changed = ebitmap_ior (dst, a, temp);
+#ifdef EBITMAP_DEBUGGING
+  {
+    ebitmap_iterator ebi;
+    unsigned int i;
+
+    EXECUTE_IF_SET_IN_EBITMAP (a, 0, i, ebi)
+      gcc_assert (ebitmap_bit_p (dst, i));
+
+    EXECUTE_IF_SET_IN_EBITMAP (b, 0, i, ebi)
+      if (!ebitmap_bit_p (c, i))
+	gcc_assert (ebitmap_bit_p (dst, i));
+    gcc_assert (changed == !ebitmap_equal_p (dst, dstcopy));
+  }
+#endif
+  ebitmap_free (temp);
+
+  return changed;
+}
+
+/* Return true if ebitmap DST is equal to ebitmap SRC.  */
+
+bool
+ebitmap_equal_p (ebitmap dst, ebitmap src)
+{
+  unsigned int i;
+  unsigned int which = MIN (dst->wordmask->size, src->wordmask->size);
+
+  if (dst->numwords != src->numwords)
+    return false;
+
+  /* sbitmap_equal compares up to the size of the first argument, so
+     if the two sbitmaps are not equally sized, we need to pass the
+     smaller one as the first argument, or it will crash.  */
+  if (which == dst->wordmask->size
+      && !sbitmap_equal (dst->wordmask, src->wordmask))
+    return false;
+  else if (which == src->wordmask->size
+	   && !sbitmap_equal (src->wordmask, dst->wordmask))
+    return false;
+
+  for (i = 0; i < dst->numwords; i++)
+    {
+      if (dst->elts[i] != src->elts[i])
+	return false;
+    }
+  return true;
+}
Index: gcc/ebitmap.h
===================================================================
--- gcc/ebitmap.h	(revision 0)
+++ gcc/ebitmap.h	(revision 0)
@@ -0,0 +1,162 @@
+/* Sparse array based bitmaps.
+   Copyright (C) 2007 Free Software Foundation, Inc.
+
+This file is part of GCC.
+
+GCC is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free
+Software Foundation; either version 2, or (at your option) any later
+version.
+
+GCC is distributed in the hope that it will be useful, but WITHOUT ANY
+WARRANTY; without even the implied warranty of MERCHANTABILITY or
+FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING.  If not, write to the Free
+Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
+02110-1301, USA.  */
+
+#ifndef GCC_EBITMAP_H
+#define GCC_EBITMAP_H
+#include "sbitmap.h"
+
+#define EBITMAP_ELT_BITS ((unsigned) HOST_BITS_PER_WIDEST_FAST_INT)
+#define EBITMAP_ELT_TYPE unsigned HOST_WIDEST_FAST_INT
+
+typedef struct ebitmap_def
+{  
+  EBITMAP_ELT_TYPE *elts;	/* non-zero element array.  */
+  unsigned int n_elts;		/* number of elements in the array.  */
+  sbitmap wordmask;		/* wordmask saying which words are
+				   non-zero.  */
+  unsigned int numwords;	/* number of non-zero words.  */
+  EBITMAP_ELT_TYPE *cache;	/* last tested element, or NULL.  */
+  unsigned int cacheindex;	/* which word cache is.  */
+} *ebitmap;
+
+
+#define ebitmap_empty_p(MAP) ((MAP)->numwords == 0)
+#define ebitmap_free(MAP)  (free((MAP)->elts), sbitmap_free ((MAP)->wordmask), free((MAP)))
+
+extern void ebitmap_set_bit (ebitmap, unsigned int);
+extern void ebitmap_clear_bit (ebitmap, unsigned int);
+extern bool ebitmap_bit_p (ebitmap, unsigned int);
+extern void dump_ebitmap (FILE *, ebitmap);
+extern void dump_ebitmap_file (FILE *, ebitmap);
+extern void dump_ebitmap_vector (FILE *, const char *, const char *, ebitmap *,
+				 int);
+extern ebitmap ebitmap_alloc (unsigned int);
+extern ebitmap *ebitmap_vector_alloc (unsigned int, unsigned int);
+extern void ebitmap_copy (ebitmap, ebitmap);
+extern void ebitmap_and (ebitmap, ebitmap, ebitmap);
+extern void ebitmap_and_into (ebitmap, ebitmap);
+extern bool ebitmap_and_compl (ebitmap, ebitmap, ebitmap);
+extern bool ebitmap_and_compl_into (ebitmap, ebitmap);
+extern bool ebitmap_ior_into (ebitmap, ebitmap);
+extern bool ebitmap_ior (ebitmap, ebitmap, ebitmap);
+extern bool ebitmap_ior_and_compl (ebitmap, ebitmap, ebitmap, ebitmap);
+extern bool ebitmap_ior_and_compl_into (ebitmap, ebitmap, ebitmap);
+extern bool ebitmap_equal_p (ebitmap, ebitmap);
+extern void ebitmap_clear (ebitmap);
+extern unsigned int ebitmap_last_set_bit (ebitmap);
+extern void debug_ebitmap (ebitmap);
+extern void dump_ebitmap (FILE *, ebitmap);
+extern unsigned long ebitmap_popcount(ebitmap, unsigned long);
+
+/* The iterator for ebitmap.  */
+typedef struct {
+  /* The pointer to the first word of the bitmap.  */
+  EBITMAP_ELT_TYPE *ptr;
+
+  /* Element number inside ptr that we are at.  */
+  unsigned int eltnum;
+
+  /* The size of the bitmap.  */
+  unsigned int size;
+
+  /* Current bit index.  */
+  unsigned int bit_num;
+
+  /* The words currently visited.  */
+  EBITMAP_ELT_TYPE word;
+
+  /* The word mask iterator.  */
+  sbitmap_iterator maskiter;
+} ebitmap_iterator;
+  
+static inline void
+ebitmap_iter_init (ebitmap_iterator *i, ebitmap bmp, unsigned int min)
+{
+  sbitmap_iter_init (&i->maskiter, bmp->wordmask, 
+		     min / EBITMAP_ELT_BITS);
+  i->size = bmp->numwords;
+  if (i->size == 0)
+    return;
+  i->ptr = bmp->elts;
+  i->bit_num = min;
+  i->eltnum = 0;
+
+  if ((min / EBITMAP_ELT_BITS) >= bmp->wordmask->n_bits)
+    {
+      i->word = 0;
+    }
+  else
+    {
+      if (TEST_BIT (bmp->wordmask, min / EBITMAP_ELT_BITS) == 0)
+	i->word = 0;
+      else
+	{
+	  unsigned int wordindex = min / EBITMAP_ELT_BITS;
+	  unsigned int count = sbitmap_popcount (bmp->wordmask, wordindex);
+	  i->word = i->ptr[count] >> (i->bit_num % (unsigned int)EBITMAP_ELT_BITS);
+	  i->eltnum = count + 1;
+	}
+    }
+}
+
+static inline bool
+ebitmap_iter_cond (ebitmap_iterator *i, unsigned int *n)
+{
+  unsigned int ourn;
+
+  if (i->size == 0)
+    return false;
+
+  if (i->word == 0)
+    {
+      sbitmap_iter_next (&i->maskiter);
+      if (!sbitmap_iter_cond (&i->maskiter, &ourn))
+	return false;
+      i->bit_num = ourn * EBITMAP_ELT_BITS;
+      i->word = i->ptr[i->eltnum++];
+    }
+
+  /* Skip bits that are zero.  */
+
+  for (; (i->word & 1) == 0; i->word >>= 1)
+    i->bit_num++;
+
+  *n = i->bit_num;
+  return true;
+}
+
+static inline void
+ebitmap_iter_next (ebitmap_iterator *i)
+{
+  i->word >>= 1;
+  i->bit_num ++;
+}
+
+/* Loop over all elements of EBITMAP, starting with MIN.  In each
+   iteration, N is set to the index of the bit being visited.  ITER is
+   an instance of ebitmap_iterator used to iterate the bitmap.  */
+
+#define EXECUTE_IF_SET_IN_EBITMAP(EBITMAP, MIN, N, ITER)	\
+  for (ebitmap_iter_init (&(ITER), (EBITMAP), (MIN));		\
+       ebitmap_iter_cond (&(ITER), &(N));			\
+       ebitmap_iter_next (&(ITER)))
+
+
+#endif /* ! GCC_EBITMAP_H */
Index: gcc/Makefile.in
===================================================================
--- gcc/Makefile.in	(revision 123086)
+++ gcc/Makefile.in	(working copy)
@@ -1152,7 +1152,8 @@ OBJS-common = \
 	version.o \
 	vmsdbgout.o \
 	web.o \
-	xcoffout.o
+	xcoffout.o \
+	ebitmap.o
 
 # Target object files.
 OBJS-md = $(out_object_file)
@@ -1745,6 +1746,8 @@ graph.o: graph.c $(SYSTEM_H) coretypes.h
     $(RTL_H) $(FUNCTION_H) hard-reg-set.h $(BASIC_BLOCK_H) graph.h $(OBSTACK_H)
 sbitmap.o: sbitmap.c $(CONFIG_H) $(SYSTEM_H) coretypes.h $(TM_H) $(RTL_H) \
     $(FLAGS_H) hard-reg-set.h $(BASIC_BLOCK_H) $(OBSTACK_H)
+ebitmap.o: ebitmap.c $(CONFIG_H) $(SYSTEM_H) coretypes.h $(TM_H) $(RTL_H) \
+    $(FLAGS_H) $(OBSTACK_H) ebitmap.h sbitmap.h
 
 COLLECT2_OBJS = collect2.o tlink.o intl.o version.o
 COLLECT2_LIBS = @COLLECT2_LIBS@

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